Cardiac troponin I-interacting kinase (TNNI3K), also known as CARK (for cardiac ankyrin repeat kinase), is a protein kinase that exhibits highly selective expression for cardiac tissues and has been shown to interact with components of the sarcomere, including troponin I (Zhao, Y. et al., J. Mol. Med., 2003, 81, 297-304; Feng, Y. et al., Gen. Physiol. Biophys., 2007, 26, 104-109; Wang, H. et al., J. Cell. Mol. Med., 2008, 12, 304-315). Although substrates for TNNI3K have not been identified to date, recent reports suggest that this protein does play a role in the development of pressure-induced cardiomyocyte hypertrophy and contractile dysfunction (Wheeler, F. C. et al., Mamm. Genome, 2005, 16, 414-423; Wang, X. et al. “TNNI3K, a cardiac-specific kinase, promotes cardiac hypertrophy in vivo”, Poster presentation at the 2006 Scientific Sessions of the American Heart Association, Chicago, Ill., Wheeler, F. C. et al., PLos Genet, 2009, 5(9), e1000647; and Pu, W. T., PLos Genet, 2009, 5(9), e1000643). Inhibition of the kinase activity of TNNI3K may disrupt these signaling pathways, and enable the mitigation and/or reversal of cardiac hypertrophy seen in patients with progressively worsening heart failure.
In response to mechanical, neurohormonal, and genetic stimuli, the heart will undergo hypertrophy, or muscle growth and remodeling, in order to maintain sufficient cardiac output to meet tissue oxygen demands. While these structural changes are initially seen as compensatory, sustained dysregulation of hypertrophic signaling can lead to heart failure, the pathophysiogical state in which the heart can no longer adequately function as a pump (Mudd, J. O. and Kass, D. A., Nature, 2008, 451, 919-928). Prevention or reversal of pathological cardiac hypertrophy has the potential to delay or prevent the development of congestive heart failure (McKinsey, T. A. and Kass, D. A., Nat. Rev. Drug Discov., 2007, 6, 617-635; Kaye, D. M. and Krum, H., Nat. Rev. Drug Discov., 2007, 6, 127-139).
Heart failure is responsible for a reduced quality of life and premature death in a significant proportion of sufferers, and is characterized by impaired cardiac function either due to reduced pump function (systolic dysfunction) or reduced filling (diastolic dysfunction). Congestive heart failure (CHF) is characterized by impaired left ventricular function, increased peripheral and pulmonary vascular resistance and reduced exercise tolerance and dyspnea. The prevalence of heart failure is anticipated to increase with aging populations, prompting a need for new and improved methods of treating heart failure.